BOILING RANGE DISTRIBUTION OF PETROLEUM DISTILLATES BY GAS CHROMATOGRAPHY: ASTM D7213
EXPLANATION
The boiling range distribution of light and medium petroleum distillate fractions provide an insight into the composition of feed stocks and products related to the petroleum refining process. This gas chromatographic (GC) method can be used to replace the conventional distillation methods. This test method extends the scope of boiling range determination by GC to include light and medium petroleum distillate fractions beyond the scope of Test Method D2887 and below Test Method D6352. The boiling range distributions obtained by this Test Method are theoretically equivalent to those obtained by true boiling point distillation (D2892). They are, however, not equivalent to results obtained from low efficiency distillation such as Test Method D86 or D1160.
This method is applicable to petroleum distillates having an initial boiling point greater than 100° C and a final boiling point less than 615° C at atmospheric pressure. This method is not applicable to petroleum distillates containing low molecular weight components such as napthas, reformats, gasolines, crude oils. Materials containing heterogeneous components, for example, alcohols, ethers, acids, or esters, or residue are not to be analyzed by this method.
TEST SUMMARY
The boiling range distribution by distillation is simulated by the use of gas chromatography. The solvent should not interfere with measurement of the samples in the 100 to 615° C range, and it should be apolar. A non-polar open tubular capillary GC column is used to elute the hydrocarbon components of the sample in order of increasing boiling point.
A sample aliquot is diluted with a viscosity reducing solvent and introduced into the GC system. Sample vaporization is provided by separate heating of the point of injection or in conjunction with column oven heating. The column oven temperature is raised at a reproducible linear rate to effect separation of the hydrocarbon components in order of increasing boiling point. The elution of sample components is quantitatively determined using a flame ionization detector. The detector signal integral is recorded as area slices for consecutive retention time intervals during the analysis.
Retention times of known normal paraffin hydrocarbons spanning the scope of this test method (C5 through C60) are determined and correlated to their boiling point temperatures. The normalized cumulative corrected sample areas for each consecutive recorded time interval are used to calculate the boiling range distribution. The boiling point temperature at each reported percent off increment is calculated from the retention time calibration.
TEST PRECISION
Repeatability of this method based on a preliminary robustness study is as follows. Reproducibility of the method is not known at present. No bias of this method can be determined because the boiling point distribution can be defined only in terms of a test method.
